Field Evaluation of Reflected Noise from a Single Noise Barrier (2018)

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19 to conduct extended monitoring at the EA-5 location, with the goal of nighttime or off-peak sampling that would allow individual vehicle pass-bys to be studied. Thus, locations SID-1, ATS-3, and EA-5 were studied in Task 5. The selected locations provided good opportunities to study the noise barrier reflections issue and offered the following characteristics: • Daily traffic volumes ranging from 18,000 to 80,000 vpd; • Cross-sections ranging from four lanes to eight lanes; • Four locations on freeways and one location on an arterial; • Four sites essentially at-grade with surrounding terrain and one location on a retaining wall; • Truck percentages ranging from 7% to 14%; • Four dense-graded asphaltic concrete (DGAC) pavements and one Portland cement concrete (PCC) pavement; • Barrier offset distances from the edge of the near travel lane ranging from 9 ft. to 96 ft.; • All barriers sound-reflective; three precast post-and-panel concrete designs, one cast-in-place concrete design, and one constructed of concrete block atop an earthen berm; and • Barrier heights ranging from approximately 12 ft. to 19 ft. Most of the measurement points were within the highway ROW, meaning that most of the distances to the community microphones were within approximately 100 ft. of the center of the near travel lane. The exception was the SR-71 site, where the more distant microphones could be set up approximately 400 ft. from the center of the near travel lane. It would have been desirable to measure farther back at other locations, but site conditions—mainly developed land uses and terrain— eliminated the ability to have distant Barrier and No-Barrier sites that were equivalent in terms of the intervening terrain. The exception was made for SR-71, where simplified model- ing (using the FHWA TNM 2.5 software) demonstrated site equivalence for frequencies of interest. Details of each location, including aerial and cross- sectional views, are presented in the balance of this chapter. I-24, Murfreesboro, Tennessee (Location BA-1, Sound-Reflecting Barrier) I-24 is an eight-lane freeway with DGAC pavement that carries 78,000 vpd with 14% trucks. The barrier is a reflective precast post-and-panel concrete wall located approximately 96 ft. from the center of the near travel lane, and it is 19 ft. tall (Figure 3). Six sound level analyzers were deployed at the BA-1 (I-24) location, three each at the Barrier and No-Barrier sites: • One reference microphone was located midway between the barrier and the edge of the roadway (BarRef01), and at a similar offset and height at the No-Barrier location (NoBarRef02). The initial plan was to locate the reference microphones 5 ft. above the top of the noise barrier at the Barrier site and at the same distance and height above the roadway at the No-Barrier site. Given the noise barrier setback, however, this first location offered a good oppor- tunity to study a point that clearly ought to be influenced by reflected noise with less masking by the direct traffic noise than the microphones across the road. • Four community microphones were placed on the opposite side of the road from the barrier, with two at the Barrier site (BarCom03 and BarCom04) and two at the No-Barrier site (NoBarCom05 and NoBarCom06). Table 4 and Figure 4 detail the microphone positions at the I-24 location. Figure 5 shows cross-sections at the Bar- rier and No-Barrier sites, and Figure 6 shows photographs of each site. Source: Research team, NCHRP Project 25-44 Figure 3. I-24—No-Barrier view (left) and Barrier view (right) at BA-1.

20 Mic. Name Side of Road (EB/WB) Distance from Center of Near Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 EB 51 (78 ft. to barrier) 10 (16 ft. above ground, near midpoint of barrier) NoBarRef02 EB 51 (78 ft. to barrier) 10 (16 ft. above ground) BarCom03 WB 84 5 (9 ft. above ground) BarCom04 WB 84 15 (19 ft. above ground) NoBarCom05 WB 84 5 (9 ft. above ground) NoBarCom06 WB 84 15 (19 ft. above ground) Table 4. I-24—microphone positions. Source: Satellite image © 2014 Google Earth Barrier Figure 4. I-24—microphone positions.

21 Figure 5. I-24—cross-sections at Barrier site (top) and No-Barrier site (bottom). At both the Barrier and No-Barrier sites, a concrete median barrier shielded the view of the vehicle tires and automo- bile engines and exhausts at the 5-ft.-high BarCom03 and NoBarCom05 microphones. The median barrier also could have shielded the BarCom03 microphone from some of the reflected noise. The I-24 measurements were conducted from 13:13 to 17:20 on August 13, 2014. The weather was partly cloudy, with alternating periods of direct sun and clouds. Temperatures were in the upper 70° F range. Winds were calm to moderate, generally coming from the northeast through the northwest. The road runs in a northwest-to-southeast direction, and the community microphones were placed on the northeast side of the road. Thus, most of the 1-minute measurement peri- ods were recorded as being in an Upwind or Calm wind class. SR-155 (Briley Parkway), Nashville, Tennessee (Location BA-3, Sound-Reflecting Barrier) Briley Parkway is a six-lane DGAC roadway on fill (a retaining wall) and carries approximately 45,820 vpd with 8% trucks (Figure 7). The barrier at this location is 12 ft. to 13 ft. high and is cast-in-place concrete with no absorptive treatment. The barrier is relatively close to the road, located on the edge of the shoulder. Only five sound level analyzers were deployed at the Briley Parkway location. The No-Barrier reference micro- phone (NoBarRef02) was not deployed because the road was on a retaining wall that was too tall to locate a micro- phone safely at the needed height above the roadway, and a microphone could not be placed safely on the road side of the barrier. Because the Barrier and No-Barrier sites were close together at the Briley Parkway location, the No-Barrier refer- ence microphone was not essential for demonstrating source equivalence with the Barrier site. Also, within the FHWA Method, one use of the No-Barrier reference microphone is to adjust the No-Barrier community microphone levels by the difference between the Barrier and No-Barrier reference sound levels. At the Briley Parkway location, the noise barrier is at the edge of a 10-ft.-wide shoulder. There was concern that any differences in the Barrier and No-Barrier reference sound levels might be caused by sound reflections between truck trailer bodies and the noise barrier, not by differences in the noise sources themselves.

22 Source: Research team, NCHRP Project 25-44 Figure 6. I-24—BarRef01 (top left), NoBarRef02 (top right), BarCom03 and BarCom04 (middle left), NoBarCom05 and NoBarCom06 (middle right), traffic video and speed (bottom left), and meteorological station (bottom right).

23 Source: Research team, NCHRP Project 25-44 Figure 7. SR-155 (Briley Parkway)—No-Barrier view (left) and Barrier BarRef01 view (right) at BA-3. Source: Satellite image © 2014 Google Earth Barrier Figure 8. SR-155 (Briley Parkway)—microphone positions. Figure 8 shows the microphone positions at the Briley Park- way location. The microphone positions were as described in Table 5. Figure 9 shows cross-sections at the Barrier and No- Barrier sites. Figure 10 shows photographs of each site. (More photographs documenting each site are provided in Appendix F, which can be viewed or downloaded from the report webpage.) The Briley Parkway noise measurements and traffic speed measurements began at 17:04 on August 14, 2014, and ended at 21:04. Operator error caused no video to be recorded. The weather was mostly calm and warm, with afternoon

24 Mic. Name Side of Road (EB, WB) Distance from Center of Near Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 EB 16 +18 (5 ft. above top of barrier) NoBarRef02 n/a n/a n/a BarCom03 WB 91* -14 (5 ft. above ground) BarCom04 WB 91* +11 (12 ft. above ground) NoBarCom05 WB 91* -14 (30 ft. above ground) NoBarCom06 WB 91* +11 (37 ft. above ground) * To retaining wall, which was topped by a safety-shaped parapet at the edge of the shoulder. Table 5. SR-155 (Briley Parkway)—microphone positions. Figure 9. SR-155 (Briley Parkway)—cross-sections at Barrier site (top) and No-Barrier site (bottom).

25 Source: Research team, NCHRP Project 25-44 Figure 10. SR-155 (Briley Parkway)—BarRef01 (top left and right), BarCom03 and BarCom04 (middle left), NoBarCom05 and NoBarCom06 (middle right), traffic video and speed (bottom left), and meteorological station (bottom right).

26 temperatures in the low 80° F range, dropping into the low 70° F range after dark. Winds were calm throughout the mea- surement period. The Briley Parkway location had a great deal of insect and tree frog noise as the late afternoon proceeded into the eve- ning. The sound level data showed unusual results; there- fore, the Briley Parkway data and results were not used in developing the findings presented in this report. A detailed discussion of the Briley Parkway data and results is provided in Appendix E. I-90, Rockford, Illinois (Location SID-1, Sound-Reflecting Barrier) I-90 is part of the Illinois Tollway system and is a six-lane freeway with DGAC pavement. It carries 53,500 vpd with 9.7% trucks. The 15-ft.-tall barrier is a reflective post-and- precast concrete wall, located 20 ft. from the center of the near travel lane. Figure 11 presents a roadside view of the barrier. Table 6 describes and Figure 12 shows the microphone positions at the I-90 location (SID-1). The video camera and Source: Research team, NCHRP Project 25-44 Figure 11. I-90—No-Barrier view (left) and Barrier view (right) at SID-1. Mic. Name Side of Road (NB, SB) Distance from Center of Near Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 SB 20 20 (5 ft. above barrier) NoBarRef02 SB 20 20 (21 ft. above ground) BarCom03 NB 69 10.4 (6.9 ft. above ground) BarCom04 NB 93 17 (15.5 ft. above ground) NoBarCom05 NB 69 10.4 (5 ft. above ground) NoBarCom06 NB 93 17 (23.5 ft. above ground) Table 6. I-90—microphone positions.

27 radar gun were located on the overpass between the Barrier and No-Barrier sites. Figure 13 shows cross-sections at the Barrier and No-Barrier sites. Figure 14 shows photographs of each site. (More photographs documenting each site are provided in Appendix F.) The I-90 measurements were taken on Decem- ber 26, 2014. Setup started at 7:00 and data collection was done from 13:00 to 17:30. SR-71, Chino Hills, California (Location ATS-3, Sound-Reflecting Barrier) SR-71 is a six-lane freeway with longitudinally grooved PCC pavement that carries 60,000 vpd with 7% trucks. The 13-ft.-high barrier consists of a 7-ft.-high reflective con- crete block atop a 6-ft.-high earthen berm wall near the ROW line at a distance of approximately 50 ft. from the center of the near travel lane (Figure 15). Table 7 describes (and Figure 16 shows) the six micro- phone positions used at the SR-71 location. The exact height of BarCom04 above the roadway plane is estimated because ground elevation data was not available. Likewise, the exact height of NoBarCom06 above the roadway plane is estimated because ground elevation data were not available. By observation in the field looking from the road, the microphone was at least 5 ft. above the roadway plane. Although having identical heights above the road would be ideal, simplified FHWA TNM 2.5 modeling (described in the spectrogram section) indicated that any effect of the height difference would be minimal in the main frequencies of interest for traffic noise. The far microphone at the Barrier site (BarCom04) was off- set from the near-roadway microphone line. The near-roadway microphone and the far microphone were strategically placed for the most meaningful comparisons to the No-Barrier data. The parameters considered in the placement were: region of barrier influence (consideration of the end of the barrier for the far-microphone position) and intervening ground (e.g., if the close microphones were placed in line with the far micro- phone, the ground between the highway noise source and BarCom03 would have included more pavement than for NoBarCom05 due to a merge lane; therefore, the close micro- phones were shifted south of where the merge lane ends). Figure 17 shows cross-sections at the Barrier and No-Barrier sites. Figure 18 and Figure 19 show photographs of each Source: Satellite image © 2015 Google Earth Figure 12. I-90—microphone positions.

28 Figure 13. I-90—cross-sections at the Barrier site (top) and No-Barrier site (bottom). site. Figure 19 shows traffic speed data collection, the traf- fic count video, and the meteorological station for this site. (More photographs documenting each site are provided in Appendix F.) On January 28, 2015, data were successfully collected at the SR-71 location from about 9:00 to 13:30, with a 15-minute to 20-minute break in the middle of this period for battery changes. The site experienced calm winds in the morning and some stronger winds toward the end of the collection period. MD-5, Hughesville, Maryland (Location EA-5, Sound-Reflecting Barrier) Maryland Route 5 (MD-5) is a four-lane arterial roadway with DGAC pavement that carries 34,200 vpd per day with 8% trucks. The 16-ft.-tall barrier is a reflective precast post-and- panel concrete wall, located approximately 9 ft. from the edge of the near travel lane (Figure 20). This road carries relatively light traffic in the nighttime hours and was studied in the evening as well as the daytime to measure individual vehicle passages. At the MD-5 location, the project team set up six micro- phone positions, as detailed in Table 8 and shown in Figure 21. In addition to the microphones, a 15-ft. meteorological tower was set up, a laser was used to measure vehicle speed, and video recordings were made to measure traffic. Figure 22 shows cross-sections at the Barrier and No- Barrier sites. Figure 23 shows photographs of each site. (More photographs documenting each site are provided in Appendix F.) The measurements were conducted on June 9, 2015. Two periods were measured. The first period, between 12:00 and 16:10, allowed for higher volume commuting traffic. The second period, between 19:40 and 23:50, allowed for lower traffic volumes and greater sensitivity to individual vehicle pass-bys. Summary of Microphone Positions for Sound-Reflecting Barriers Table 9 and Table 10 summarize the microphone heights and distances from the road at each location.

29 Source: Research team, NCHRP Project 25-44 Figure 14. I-90—BarRef01 (top left), NoBarRef02 (top right), BarCom03 and BarCom04 (middle left), NoBarCom05 and NoBarCom06 (middle right), traffic video and speed (bottom left), and meteorological station (bottom right).

30 Source: Research team, NCHRP Project 25-44 Figure 15. SR-71—No-Barrier NoBarCom05 view (left) and Barrier BarRef01 view (right) at ATS-3. Mic. Name Side of Road (NB, SB) Distance from Center of Near Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 NB 25 10 (10 ft. above ground) NoBarRef02 NB 25 10 (10 ft. above ground) BarCom03 SB 25 10 (10 ft. above ground) BarCom04 SB 400 Approximately 17 (10 ft. above ground) NoBarCom05 SB 25 10 (10 ft. above ground) NoBarCom06 SB 400 At least 5 (32 ft. above ground) Table 7. SR-71—microphone positions.

31 Source: Satellite image © 2015 Google Earth Figure 16. SR-71—microphone positions.

32 Figure 17. SR-71—cross-sections at Barrier site (top) and No-Barrier site (bottom).

33 Source: Research team, NCHRP Project 25-44 Figure 18. SR-71—BarRef01 (top left), NoBarRef02 (top right), BarCom03 (middle left), BarCom04 (middle right), NoBarCom05 (bottom left), and NoBarCom06 (bottom right).

34 Source: Research team, NCHRP Project 25-44 Figure 19. SR-71—BarRef01 traffic speed (top left), traffic count video (top right), and meteorological station (bottom).

35 Source: Research team, NCHRP Project 25-44 Figure 20. MD-5—No-Barrier NoBarCom05 and NoBarCom06 view (left) and Barrier view from meteorological station (right) at EA-5. Mic. Name Side of Road (NB, SB) Distance from Center of Near Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 SB 15 17.5 (5 ft. above barrier) NoBarRef02 SB 18 17.5 (18 ft. above ground) BarCom03 NB 80 5 (9 ft. 3 in. above ground) BarCom04 NB 80 15 (19 ft. 3 in. above ground) NoBarCom05 NB 69 7 (5 ft. above ground) NoBarCom06 NB 69 17 (15 ft. above ground) Table 8. MD-5—microphone positions.

36 Source: Satellite image © 2015 Google Earth Figure 21. MD-5—microphone positions.

37 Figure 22. MD-5—cross-sections at Barrier site (top) and No-Barrier site (bottom).

38 Source: Research team, NCHRP Project 25-44 Figure 23. MD-5—BarRef01 (top left), NoBarRef02 (top right), BarCom03 and BarCom04 (middle left), NoBarCom05 and NoBarCom06 (middle right), traffic speed (bottom left), traffic video (bottom middle), and meteorological station (bottom right).

39 Microphone Name Distance (ft.) I-24 SR-155 (Briley Pkwy.) I-90 SR-71 MD-5 Travel Lane Barrier Travel Lane Barrier Travel Lane Barrier Travel Lane Barrier Travel Lane Barrier BarRef01 33 45 0 0 4 0 9 19 2 0 NoBarRef02 33 45 n/a n/a 4 0 9 19 3 0 BarCom03 66 285 75 180 53 180 9 165 64 175 BarCom04 66 285 75 180 77 205 384 540 64 175 NoBarCom05 66 285 75 180 53 180 9 165 53 175 NoBarCom06 66 285 75 180 77 205 384 540 53 175 Table 9. Distance (ft.) from microphone to center of near travel lane and barrier. Microphone Name Distance (ft.) I-24 SR-155 (Briley Pkwy.) I-90 SR-71 MD-5 GND RD GND RD GND RD GND RD GND RD BarRef01 16 10 23 18 20 20 10 10 17.5 17.5 NoBarRef02 16 10 n/a n/a 21 21 10 10 18 17.5 BarCom03 9 5 5 -14 6.9 10.4 10 10 9.3 5 BarCom04 19 15 12 11 15.5 17 10 17 19.3 15 NoBarCom05 9 5 30 -14 5 10.4 10 10 5 7 NoBarCom06 19 15 37 11 23.5 17 32 5 15 17 Table 10. I-24 and SR-155 (Briley Parkway)—Microphone heights (ft.) from ground (GND) and roadway (RD).

40 Sound-Absorbing Barrier Study Locations Selected Locations The Phase 1 location selection criteria were used for Phase 2. These criteria were used to judge if a Barrier site and its potentially equivalent No-Barrier site are indeed equiva- lent. Consultation with state highway agency officials and web-based mapping reviews identified candidate locations. Field reviews were then conducted at the most promising locations. A final set of three locations was identified. 1. OH-1, I-75, Troy, Ohio: This six-lane freeway has a sound-absorbing 16–18 ft. precast concrete-based post- and-panel noise barrier that is set back 50 ft. from the edge of the nearest travel lane. The road carries more than 63,000 vpd with a high percentage of trucks (21%). 2. OH-2, I-70, South Vienna, Ohio: This six-lane freeway has a sound-absorbing 18–20 ft. precast concrete-based post-and-panel noise barrier that is set back 80 ft. from the edge of the nearest travel lane. At nearly 46,000 vpd, this location carries less traffic than does the I-75 location, but I-70 has heavy truck traffic at 30% of the total volume. 3. OH-3, I-270, Grove City, Ohio: This six-lane freeway has a sound-absorbing 14–16 ft. precast concrete-based post- and-panel noise barrier that is offset 12–20 ft. from the edge of the near travel lane. I-270 carries nearly 64,000 vpd, with approximately 29% trucks during the nighttime period when noise measurements were taken at this location to study individual vehicle pass-bys. Table 11 details the characteristics of these selected locations, summarized as follows: • Daily traffic volumes range from 46,000 vpd to 64,000 vpd; • The cross-sections are all six-lane highways, with one being at-grade, one with the ground slightly elevated at the microphone positions, and one with the terrain varying from slightly above to slightly below the roadway elevation; • Truck percentages are high; • One of the pavements is dense-graded asphalt and two are concrete; • Barrier offset distances range from a position at the edge of the pavement to a position near the ROW line; • All three barriers are precast concrete post-and-panel designs, with sound-absorbing faces on the highway side; and • Barrier heights range from approximately 14 ft. to 20 ft. The I-75 and I-270 locations had microphone positions both on and off the ROW, while the I-70 location had all microphones on the ROW due to the heavy vegetation off the ROW. The noise measurement data indicated that the presence of houses near the more distant microphone at the No-Barrier site appears to have been a source of reflected traffic noise that was not apparent in the field review dur- ing the location selection process. Details of each location, including aerial and cross-sectional views, are presented in subsequent sections of this chapter. I-75, Troy, Ohio (Location OH-1, Sound-Absorbing Barrier) As shown in Figure 24, the I-75 location is a six-lane free- way. The barrier is approximately 3,370 ft. long, 15 ft. high, and offset 50 ft. from the edge of the nearest travel lane. The barrier is a precast concrete post-and-panel design with a proprietary sound-absorbing face made using recycled rub- ber tire chips on the highway side. Sound-absorption test results were not available for this barrier; however, results for a comparable panel from the same company (using the same sound-absorbing product) had demonstrated the sound- absorption coefficients shown in Table 12. Figure 25 shows a site map of the measurement positions for the Barrier microphones (BarCom and BarRef), No-Barrier microphones (NoBarCom), the speed and traffic video site, C H A P T E R 4

41 Location Roadway City, State Road Class Lanes Pavement Type Geometry Relative to Adjacent Land Uses AADT (vpd) and Year Percent Trucks Barrier Location Barrier Material Barrier Height at Study Site (ft.) OH-1 I-75 Troy, OH Freeway 6 PCC At-Grade 63,273 (2015) 21% ROW Concrete with rubber tire chip sound- absorbing face 16–18 OH-2 I-70 South Vienna, OH Freeway 6 DGAC Slight cut 45,923 (2015) 30% ROW Concrete with rubber tire chip sound- absorbing face 18–20 OH-3 I-270 Grove City, OH Freeway 6 PCC At-Grade 63,768 (2015) 29% (sampling 24:00– 04:00) EOP Concrete with wood fiber aggregate sound- absorbing face 14–16 Table 11. Selected Phase 2 sound-absorbing barrier locations. Source: Research team, NCHRP Project 25-44 Figure 24. I-75—No-Barrier view (top left), Barrier view (top right), roadway close-up (bottom left), and highway-side Barrier close-up (bottom right).